The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Electronically-scanned antennas (ESAs) combine a wide range of electrical and mechanical functions to produce agile directional beam steering. ESAs require complex radio frequency (RF) distribution networks as well as direct current (DC) power and logic that must be routed to the typical unit cell. The unit cell is the building block of an ESA comprised of amplification, attenuation, phase-shifting, logic control, etc., and serves as the point of contact to free-space through a radiating element. For full-duplex communication applications, the unit cell provides either a transmit or a receive function. The unit cell functions of the specific antenna application, e.g., power out, phase shifting, attenuation, control, etc., generally define the number, type and dimensions of the unit cell beam scanning electronic elements required. Depending on the operating frequency, scanning angle and type of function of the specific antenna application, the required beam scanning electronic elements may require more or less space and area that directly affect the size of the unit cell and more importantly, the size of the antenna face, i.e., the antenna aperture.
The ESA scanning performance is directly dependent upon the array lattice dimensions. Typically, the radiating element array lattice dictates the general geometry of the unit cells. Thus, based on the desired antenna performance requirements for the specific application, the larger the radiating element array lattice and the more complex the desired antenna specifications, the greater the number of beam steering electronics and the tighter the packing of the associated unit cells. This significantly affects the cost and manufacturability of the ESA. Various cost-saving measures have been employed to reduce such incurred costs. For example, thinning the number and randomizing the unit cell orientations and locations have been employed to reduce the number of unit cells and their packing density, while maintaining acceptable scanning properties of the ESA. The number of elements, geometry and packing density of the radiating element array lattice are directly dependent on the desired beam scanning properties of the ESA. The tighter the lattice, the better the ESA will scan. It has been established that a half-wavelength spacing between the radiating elements at the upper end of a typical operating bandwidth provides excellent beam steering performance, but requires greater packaging complexity.
To enable more functions, wider scanning requirements and higher operating frequencies of an ESA, unit cell packaging solutions are required that address such things as radiation performance over bandwidth; vertical transition fabrication, assembly and reproducibility; DC power distribution (e.g., V+, V− power planes); logic control distribution (e.g., data and clock); RF distribution for wider instantaneous bandwidths; efficient thermal management of the unit cells; mechanical integrity and robustness of the unit cells under shock, vibration, and environmentally harsh conditions (e.g., humidity, salt fog, etc). Some efforts to integrate functions and reduce the overall parts count and cost have resulted in multi-element module architectures. However, due to the increased complexity of the number of beam steering elements needed in the unit cells, such known architectures require gaps between radiating elements that are larger than the aforementioned half-wavelength spacing. Thus, beam steering performance is greatly degraded
Accordingly, there is a need for a packaging architecture for a phased array antenna module which permits even closer radiating element spacing to be achieved, and which allows for even simpler and more cost efficient manufacturing processes to be employed to produce a phased array antenna.